Process of tanning.



W. PETRIE'.

PROCESS OF TANNING.

APPLICATION FILED APR.2. 191

Patented July 23, 1918.

WALTER PETRIE, 0F ENIDICOTT, NEW YORK, ASSIGNOR TO PETRIE PROCESSCOMPANY, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

PROCESS OF TANNING.

Specification of Letters Patent.

Patented July 23, 1918.

Application filed April 2, 1917. Serial No. 159,226.

- To all whom it may concern:

Be it known that I, WALTER Pn'rmn, a subject of the King of GreatBritain and Ireland, residing at Endicott, in the county of Broome andState of New York, have invented certain new and useful Improvements inProcesses of Tanning, of which the following is a specification.

This invention relates to processes of tanning; and it comprises amethod of producing a quick tanning operation wherein hide, which isadvantageously first set, that is treated with tanning solution enoughto prevent pebbling or rainin in the subsequent operation, is wor ed wita small quantity of a strong tanning solution, such strong tanningsolution being progressively added thereto in small successive portionsand the working being advantageously in a drum or the like, the amountof such tanning solution supplied being that which suflices for completetanning and the strength being such that no substantial excess of liquoror solution remains after the operation, the whole operation beingconducted under such conditions as will give suflicient ventilation forcooling and evaporating purposes; all as more fully hereinafter setforth and as claimed.

In tanning hides to make leather, all sorts of materials are employed tomake the tanning liquors, a tanning action being by no means restrictedto what are chemically known as the tannins. Thesetanning solutionscontain materials which have a marked aflinity for the hide substanceand which may be here called tans and bodies which have not this markedaffinity and may be called non-tans. The latter substances however areuseful in the leather. In the customary methods of tanning, the hidesare treated with a large volume of the tanning liquor, whatever it maybe the bath being replenished with new extract from time to time.Fromthis large volume the hides selectively absorb the tans inpreference to the non-tans and the non-tans consequently accumulate asthe liquor grows older. In the course of time the character of theliquor therefore is apt to change materially. In the tanning, for'thesake of quickeningthe action, agitation of. one kind or another is verycommon. Very frequently the hides are placed in a rotating drumcontaining a large body of liquor. he agitation due to rotationmaterially accelerates the absorption. In view of the large volume ofliquor usually employed it is not customary to have it veryconcentrated; it is, relatively speaking, usually rather dilute. Tanningprocesses now customary are generally relatively slow. It is the objectof the present invention to provide a quicker tanning more or less wet,adding new concentrated liqu'or as thelhides require it. In so doing Iuse a type of drum somewhat different from those heretofore employed fortannin pur: poses, providing means for free venti ation. The ventilationmay be that due to natural circulation of air through openings in thedrum or it may be a forced ventilation made by passing air through bymeans of a fan or the like. This free ventilation keeps the materialfrom heating up or becoming warm and also has a useful effect inremoving water as vapor, keeping the liquor concentrated. Ordinarily Iuse merely the amount of strong liquor which will suflice for a completetanning; using the liquor of such strength that after my operation iscompleted there is substantially no excess. If there should chance to bea little excess it does no harm since it can be reused; but ordinarily Iuse just about the amount of liquor which will be absorbed by the hides,allowing for loss due to evaporation. In this method of'operation, sinceI am causing the hide to absorb substantially all the liquor, the liquorI employ must be sufliciently concentrated to afford all the tans andnontans which it is desired to have taken up by the hide. By the use ofstrong tan liquors I much accelerate the absorption, while the coolinggiven by the free ventilation and incident evaporation preventsdevelopment of heat and injury to the hides. The evaporation alsooperates to concentrate the liquor further and insure completeabsorption. Since the present method puts substantially all the solublesof the extract into the hide, preventing the stated differentialabsorption f t n a the exp f o I also seabout 24 to.36 hours.

cure a better utilization of my extract, a greater weight of leather anda uniform product, my product not varying from week to week as is thecase in tanning with baths of changing composition.

In the present invention the hides are ordinarily first set in a tanningsolution, the object of this preliminary treatment not being to tan thehides to any extent but merely to set them enough to prevent graining,etc., in'the tanning operation proper; 2'. 6., prevent the surface frombecoming puckery or coarse grained. I may take the hides from the beamhouse and tan them. The hides coming from the setting process which arewet and 1 contain dilute tanning solution are put into a drum togetherwith a little strong tanning solution, say for a 7-foot. drum containing1,500 pounds (wet weight, or what is known as white weight amongtanners) I add first about 15 to 25 gallons, say 20 gallons of a strongtanning solution, say 220 barkometer or about 30 B6. The drum isprovided with means causing or allowing free ventilation. The drum isrotated and the liquor is taken up by the hides, Evaporation takesplace, strengthening the liquor, this evaporation being aided by thefree ventilation. As the liquor is absorbed, new strong liquor is added,the time when additions are necessary being judged by the appearance ofthe leather and liquor. Ordinarily, additions of liquor in smallportions are continued at intervals of about 18 to 24:.hours, thisdepending upon the thickness, etc., of the hides; a final period ofabout 6 to 10 hours rotation being given during which no additions aremade. This results in a completely tanned leather with substantiallycomplete absor tion of theliquor or extract used. The comp ete drummingoperation takes from At no time is there more than enough liquor in thedrum than will suffice to keep the leather wet and furnish a little free.liquid. The. hides are not submerged; neither is a great excess ofliquor ever prefint. Under the conditions, in order toprevent heatingthere must be, as stated, free ventilation or other methods of cooling.

In the described operation it is better that the materials besomewhatacid; but theamount of acid needed is not great. I do not ordinarilyacidify during the tanning operation proper but rely on the presence ofenough acid in the hide from the preliminary operation hereinafterdescribed.

The acidity may be that due to any mineral or organic acid.

While a wide variety of tanning materlals may be employed in thedescribed process, I find that I can operate it very advantageously withvarious tanning materials comprising or consisting of preparations fromwaste sulfite liquor; and particularly that known in the trade as spruceextract. Spruce extract is a somewhat acidified concentrated wastesulfite liquor. Instead of, or in addition to, spruce extract, however,I may use quebracho, oak, cutch, hemlock, chestnut extracts, etc., orany other well known tanning material. Blends of the various tanningextracts may also be employed.

In an advantageous embodiment of the present invention I take the wethides com ing from the beam house and first color them. This may be doneby any of the usual methods. A good way of doing it is to treat thehides with spruce extract with which may or may not be mingled othertanning materials. Ordinarily I next treat with an acid bath. Any of theordinary organic or inorganic acids may be em-' ployed. A bath of watercontaining about.- 02 per cent. sulfuric acid will serve, In this baththe hides may be hung for 24: hours or thereabouts. The hides are nexttreated in a setting bath which advantageously contains more or lessspruce extract. An advantageous strength or solution in the settingoperation, using spruce extract, is about 65 barkometer, or, around 9Be. It is advantageous to leave the hides in the setting bath for atleast two or three days. If desired, the setting bath and the acid bathmay be combined, the setting bath being simply acidified with anyconvenient acid. From the setting bath the material 100 next goes to arotary drum provided with ventilating means of some type wherein itis-treated with successive small additions of concentrated tanningliquor; this concentration being advantageously as high as 220barkometer. So to speak, the hide is fed with very strong liquor atabout the rate the liquor disappears. The total amount .of this liquoremployed may be about equal to the white weight of the hides. After thedrumming operation is complete the leather may be finished in any of thewell known ways The present process gives a'good yield of good leatherin about six days from beam house to bleach. While not in any wayrestricted to sole leather making, it is particularly advantageoustherein. In acid sole leather making, it may be applied to the stockfrom either the first lay-aways or the I larged scale showing theventilating opening and the splash plate.

In this showing 1 indicates an imperforate drum mounted in bearings 2and 3 and provided with trunnions 4 and 5. Pulley (i is keyed to onetrunnion. The ends of the drum are provided with openings as at 7 andwith dams or splash plates 8 mounted inside the drum by means of bolts 9and nuts 10 and washers 11. The splash plates are spaced a slightdistance from the openings and practically overlap them to some extent.The liquor is introduced into the drum through pipe 12 leading from thesource of supply. The interior of the drum is provided with a pluralityof pins 13 which serve to catch the hides and assist the tumblingaction, the hides being diagranv matically represented in the drum byreference character 14; The operation of this drum is obvious from theforegoing description.

lVhat I claim is 1. The process of tanning hides which comprisestreating a hide with a small quan tity of strong liquor under conditionspromoting free evaporation and cooling thereby, and successivelysupplying fresh small portions of liquor as previous additions tend todisappear by absorption and evaporation until the full quantity ofliquor has been supplied and the hide is tanned.

2. The process of tanning hides which comprises agitating the hides inthe presence of a small quantity of strong liquor in an apparatuspermitting circulation of air thcrethrough and supplying freshquantities of liquor as the liquor is absorbed.

In the tanning of hides the process which comprises substantiallycompletely absorbing an amount of strong liquor less than that necessaryto completely tan the hide and subsequently subjecting the hide to afurther quantity of strong liquor, and during the process agitating andcooling the hide.

l. The process of tanning hides \VlllCll comprises agitating the same ina rotary drum in the presence of an amount of highly concentratedtanning liquor less than that necessary to completely tan the hide, ad-1nitting-air to the hides during the rotation of the drum to evapo atemoisture and cool the hide, and adding further amounts of strong tanningliquor.

5. The process of tanning hides which comprises agitating hides with asmall constantly renewedquantity of strong tanning liquor, the amount ofsuch liquor present at any one time being insullicient to prevent freeaccess of air to said hides.

In testimony whereof I ailix my signature hereto.

' WALTER PETRIE.

